The present invention relates to a fork lift with a laterally traveling system which can switch the fork lift to lateral running.
Conventionally, vehicles having a laterally travelling system have been seen among large-scale transporters, some kinds of loaders and the like, and reach-type electric vehicle type fork lift devices. Furthermore, there are also side fork lifts for handling long materials, which have a mast or forks installed in a lateral direction with respect to the movement of the vehicle. However, there is no counter-type fork lift which has a function similar to that of a side fork capable of lateral moving in addition to ordinary operational functions. In order to achieve a fork lift of such kind, it is necessary to steer front wheels which are drive wheels in a perfectly lateral direction.
More specifically, in a conventional fork lift 1 as illustrated in FIG. 23, a pair of right and left-hand front wheels (drive wheels) 3 are provided to a front portion of a vehicle 2, a pair of right and left-hand rear wheels (steering wheels) 4 are provided to a rear portion thereof, and a driver""s room 5 is provided above the front portion of the vehicle 2. A vertically extendable mast 6 is provided in the front end section of the vehicle 2 to be rotatable in the front-and-rear direction by means of a coupling axle 7 extending in the lateral direction of the vehicle, and a tilt cylinder 8 for performing front-and-rear rotation is provided between the vehicle 2 and the mast 6.
The mast 6 comprises a pair of right and left-hand outer frames 9 on the fork lift 1, and a pair of right and left-hand inner frames 10 guided on the outer frames 9 to be able to move vertically, a lift cylinder 11 provided between the outer frames 9 and inner frames 10. Furthermore, a lift bracket 12 guided by the inner frames 10 to be able to move vertically is provided, and a pair of right and left-hand forks 13 are provided to this lift bracket 12 via a pair of upper and lower finger bars.
A seat 15, and a handle 16 or the like disposed to the front of this seat 15 are provided in the driver""s room 5, and above these elements, a head guard 19 is provided via front pipes 17 and rear pipes 18 projecting from the vehicle body 2. A counter weight 20 is provided on the vehicle body 2, to the rear of the seat 15.
However, in the conventional fork lift 1 described above, since the right and left-hand front wheels 3 are driven by a common travel drive, it is not possible to steer these front wheels 3 in a perfectly lateral direction, and hence lateral running cannot be achieved.
Therefore, it is a first object of the present invention to provide a fork lift with a laterally travelling system so that the front wheels forming the drive wheels can be steered to face directly sideways, whilst being capable of performing ordinary fork operations.
It is a second object of the present invention to provide a fork lift with a laterally travelling system which allows adjustment of linear movement and change of the direction of the vehicle body during lateral running.
It is a third object of the present invention to provide a fork lift with a laterally travelling system which permits the vehicle to readily turn during lateral running.
It is a fourth object of the present invention to provide a fork lift with a laterally travelling system which allows the front wheels to steer, with the mast being disposed between the right and left-hand front wheels.
In order to achieve the first object described above, the fork lift with a laterally travelling system according to the present invention is characterized in that a pair of right and left-hand front wheels and a pair of right and left-hand rear wheels are provided in a steerable fashion on a vehicle body, the pair of right and left-hand front wheels are coupled respectively to driving shafts of travel drive devices, both travel drive devices are installed on turning members provided rotatably about a vertical axis with respect to the vehicle body, rotating means for performing rotation of the turning members is provided, a mast is provided on the front end of the vehicle body, and forks are provided on the mast.
According to the present invention described above, during normal running, the right and left-hand front and rear wheels face in the front-and-rear direction. Thereupon, by operating a lift lever, the forks are raised or lowered along the mast, and prescribed fork operations can be performed. When switching from normal running to lateral running, rotating means is actuated first and the turning members are rotated about the vertical axis, whereby the front wheels can be steered (to be in a perfectly lateral direction) with respect to the vehicle body. Here, since the front wheels are respectively formed integrally with running drive devices, it is possible to perform this turning operation readily and smoothly. After steering the front wheels in a perfectly lateral direction in this manner, the fork lift can be caused to run laterally in the right and left direction, by driving the front wheels in the forward and reverse directions by means of the travel drive devices. In so doing, follow-up steering of the rear wheels is effected by means of a turning caster system, or alternatively, the rear wheels are steered forcibly in a similar manner to the front wheels.
In this way, in the present invention, it is possible to perform lateral running by steering the driving front wheels so as to face in a perfectly lateral direction, while using normal fork operations. Hence it is possible to readily convey long materials, for example, by means of the forks.
In order to achieve the second object described above, in the first aspect of the fork lift with a laterally travelling system according to the present invention, the rotating means is constituted such that the two turning members are operated to turn in mutually opposing directions by means of a common actuation device.
According to this first aspect of the invention, when switching from normal running to lateral running, it is possible to steer the front wheels (to a perfectly lateral direction) with respect to the vehicle body by actuating the common actuation device of the rotating means so as to rotate the turning members in mutually opposing direction about the vertical axes. In this manner, after steering the front wheels to a perfectly lateral direction, the fork lift can be made to run laterally in the right and left direction, by controlling and rotating the front wheels in mutually opposing directions by means of the travel drive devices.
Moreover, when performing lateral running, in other words, in lateral running mode wherein the two front wheels are steered laterally with respect to the vehicle body, it is possible to readily correct deviation caused in the linear movement of the vehicle by road surface conditions or the weight balance of the vehicle, by slight actuation of the actuation device to steer the two front wheels inwards or outwards by a small angle. Moreover, by steering the front wheels inwards or outwards, the direction of the fork lift can also be changed to some extent during lateral running, and hence steering during lateral running can be performed.
Moreover, in a second aspect a fork lift with a laterally travelling system according to the present invention, the rotating means comprises coupling sections of the turning members disposed in mutually opposing directions in the front-and-rear direction with respect to the vertical axis; a link member in the lateral direction of the vehicle, the link member being coupled between these coupling sections to enable the turning members to be relatively rotatable; and an actuation device for moving this link member in the lateral direction of the vehicle.
According to this second aspect of the invention, it is possible to steer the front wheels readily and reliably with respect to the vehicle body by moving the link member in the lateral direction of the vehicle, by means of the actuation device.
In order to achieve the third object described above, in the third aspect of the fork lift with a laterally travelling system according to the present invention, when the rotating means is operated to rotate the turning members, the two drive wheels laterally directed are displaced in the front-and-rear direction.
According to this third aspect of the invention, by controlling and rotating the drive wheels by means of the travel drive devices, after the drive wheels have been steered to be in perfectly lateral directions, in other words, by controlling and rotating the right and left-hand drive wheels in such a manner that the rotational directions and the speeds of revolutions thereof are the same, the fork lift can be made to travel laterally in a right and left direction. Moreover, since the two drive wheels steered directed to be perfectly lateral are displaced in the front-and-rear direction of the vehicle, when performing lateral running, a turning force to the right or left can act on the vehicle, by simply differentiating the speeds of revolutions of the right and left-hand drive wheels by operating a handle or the like. Hence, lateral running can be performed while steering the vehicle readily in the longitudinal direction (front-and-rear direction) thereof, and any deviation caused in linear movement of the vehicle by the road surface conditions or the weight balance can be readily corrected.
In order to achieve the fourth object described above, in a fourth aspect of a fork lift with a laterally travelling system according to the present invention, the mast is installed between the right and left-hand front wheels at the front end of the vehicle to be rotatable in the front-and-rear direction by means of a coupling axle disposed in the lateral direction of the vehicle above the front wheels, a rotational drive device for effecting front-and-rear rotation is provided between the vehicle body and the mast, and when the mast is rotated by this rotational drive device, the lower section of the mast is moved to a position where the mast does not interfere with the steering of the front wheels.
According to this fourth aspect of the present invention, during normal running, the mast assumes an upright attitude, the lower section thereof being disposed between the right and left-hand front wheels, and hence the fork lift can be formed without creating a long front overhang. The operation of switching from normal running to lateral running can be performed by rotating (inclining) the mast about the coupling axle by operating the rotating drive device and moving the lower section thereof to a position where the mast does not interfere with the steering of the front wheels, steering the front wheels to a 90xc2x0 position (to be directed laterally) with respect to the vehicle body, and rotating the mast about the coupling axle by reverse operation of the rotating drive device to return the mast to the upright attitude. Thereby, the fork lift can be made to travel laterally, while performing smooth turning without any hindrance and without creating a long front overhang.